Presently, limitations of 3D motion capture systems used in the medical field, sports analysis, and in special effects for movies and video games Include: l) indirect Identification of markers, 2) minimum of 2 video camera requirement to capture any marker, and 3) loss of valuable data due to occlusions and merging. The Doppler properties of radio frequency (RF) signals, and digital and wireless communication technologies can overcome these limitations. This investigation will use the Doppler shift of an RF signal and digital communication techniques to develop a low cost, highly accurate and versatile 3D motion capture system. [unreadable] [unreadable] Specific Aim I: Develop/Test 2D Angle Measurement. Task 1: Build the 2D device. A Doppler transmitter unit will be constructed to send an RF signal to a miniature receiver sensor. Virtual movement of the transmitting antenna creates a Doppler shift in the signal at the receiver sensor. Task 2: Evaluation of the 2D device. The ability of a transmitter receiver unit to measure angle will be systematically tested using known angular positions, and both static and dynamic [unreadable] tests. [unreadable] [unreadable] Specific Aim II: Develop/Test 3D Position Measurement. The basic transmitting-receiving system developed in Aim 1 to measure angle will be expanded in Aim 2 to determine 3D position and orientation. Task 1: Build the 3D device. A Doppler transmitter unit, rotating in two orthogonal planes (vertical and horizontal) and a receiver sensor triad will be used to capture 3D position and orientation. The known separation between the sensor triad antennas and the signals it receives will be the basis for the 3D position and orientation calculations. Task 2: Evaluation of the 3D device. The ability of a transmitter-receiver system to measure position and orientation will be systematically tested using known positions, and numerous static and dynamic tests. [unreadable] [unreadable]